1. Field of the Invention
The present invention relates to magnet wire having a bondable coating thereon and more particularly to bondable magnet wire finding particular, but not necessarily exclusive utility for the coil windings of dynamo electric machines adapted for use in hermetic atmospheres.
2. Description of the Prior Art
Magnet wire including a bondable overcoat has been described in the art. See, for example U.S. Pat. No. 2,916,403, issued Dec. 8, 1959, to G. C. Calderwood, for BONDING COMPOSITIONS; U.S. Pat. No. 3,456,338, issued July 22, 1969, to D. W. Mohrman, et al., for METHOD FOR CHANGING THE CONFIGURATION OF AND FOR BONDING ELECTRICAL COILS OF INDUCTIVE DEVICES; U.S. Pat. No. 3,300,843, issued Jan. 31, 1967, to T. Umewaka, et al., for SELF BONDING MAGNET WIRE AND METHOD; U.S. Pat. No. 3,516,858, issued June 23, 1970, to A. F. Fitzhugh, et al., for SELF-BONDING MAGNET WIRE AND PROCESS FOR PREPARING THE SAME; U.S. Pat. No. 3,676,814, issued July 11, 1972, to F. F. Trunzo, et al., for HIGH TEMPERATURE ADHESIVE OVERCOAT FOR MAGNET WIRE; and U.S. Pat. No. 4,152,103, issued May 1, 1979 to R. H. Napierski, for DEVICE FOR BAKING SELF-BOND COIL WIRE.
Polyesterimide wire enamels are well-known and widely used in the art of forming magnet wire for high temperature hermetic applications. Compositions and methods for forming polyesterimide wire enamels are well-known, and the application thereof to wire to form magnet wire is conventional and well-known to those of ordinary skill in the art.
Synthetic polyester resin wire enamels are also known and widely utilized. One particularly successful polyester magent wire insulation resin is manufactured by the General Electric Company under the Trademark ALKANEX, and is disclosed in U.S. Pat. No. 2,936,296, issued May 10, 1960, to F. M. Precopio, et al., for POLYESTERS FROM TEREPHTHALIC ACID, ETHYLENE GLYCOL, AND A HIGHER POLYFUNCTIONAL ALCOHOL.
Polyamide-imide wire enamels are known and widely used in the art of producing magnet wire. See, for example, U.S. Pat. No. 3,428,486, issued Feb. 18, 1969, to N. J. George, for POLYAMIDE-IMIDE ELECTRICAL INSULATION; U.S. Pat. No. 3,475,212, issued Oct. 28, 1969, to H. J. Bach, for METAL CONDUCTOR COATED WITH NONLINEAR COPOLYESTER BASECOAT LAYER AND POLYAMIDE-IMIDE OUTER LAYER; U.S. Pat. No. 3,528,852, issued Sept. 15, 1970, to E. H. Olson, et al., for DUAL-COATED ELECTRICAL CONDUCTOR; and U.S. Pat. No. 3,695,929, issued Oct. 3, 1972, to F. A. Sattler, for CONDUCTORS INSULATED WITH A POLYMERIC AMIDE-IMIDE-ESTER AND AN AROMATIC POLYIMIDE OR AROMATIC POLYAMIDE-IMIDE OVERCOAT. Polyamide-imide wire enamels are conveniently applied from solutions of the polymer in a solvent, such as n-methyl pyrrolidone (NMP). For a discussion of the effect of residual solvent on the properties of cured polyamide-imide coatings, see P. Bailey and J. N. Communal, Revue Generale De L'Electricite, February 1978, Vol. 87 #2 at pages 149-159, at pg. 152.
The polyamide-imide enamel coating is conventionally applied to the wire substrate from a solution of the polyamide-imide in a suitable solvent, such as N-methylpyrrolidone (NMP), in a conventional wire tower, such as shown for example, in U.S. Pat. No. 3,183,604, issued May 18, 1965, to J. D. Stauffer, for APPARATUS AND PROCESS FOR REMOVING SOLVENTS FROM COATINGS ON METAL; U.S. Pat. No. 3,183,605, issued May 18, 1965 to D. D. Argue, et al., for APPARATUS FOR COATING METALS; and U.S. Pat. No. 3,351,329, issued Nov. 7, 1967, to D. W. Thomas, for WIRE COATING OVEN APPARATUS.